white scale on comb

i have a 10 month old chicken not eating or drinking as well as usual, huddling against wall, pale comb with white scale--some balding around head and eyes, missing feathers in front of tail, some picking at herself--wt loss--i have looked at mites, lice, pox, etc and not sure of a matching disease. i don't see anything moving on her skin or around her eyes. i have ordered d.e. to treat the chix and the coop--any experts that could give me ideas
about what may be wrong?

just an update: i finally spotted tiny black mites (?) crawling quickly on the part by her tail that is balding and on her comb. i put vaseline on the balding spot and dusted her--she is separated from the others and she at least is standing, eating and drinking. i don't know if she will live or not but i will treat the flock and the coop.